The present invention relates to a portable electric power source useful in operating battery powered devices and having particular utility in the operation of devices of an emergency type nature, such as for example paging devices.
In recent years the use of portable paging devices by business and service personnel as well as doctors, volunteer firemen and others subject to emergency calls, has substantially increased. In addition to the wider use of such devices, the devices themselves have become smaller, lighter, and more versatile, to the point where they no longer merely alert the carrier to the fact that he has a call, but can even provide the number to which he is to respond.
As such devices have become more compact, the power supply has also, out of necessity, had to be reduced. Such devices now typically operate on a single standard AA cell. Unfortunately, there is no way to determine the useful life remaining in the cell at any given time. This can create a serious, even life threatening problem, i.e. the doctor whose pager has become inoperative, being out of touch with his emergency service until he is able to obtain a new battery. This can leave a doctor or other individual out of communication for a relatively long, potentially critical period of time.